The invention relates to a heater for heating an advancing, thermoplastic yarn.
Such a heater is known from EP 412 429 and corresponding U.S. Pat. No. 5,148,666. It has the disadvantage that the curvature of the yarn path is invariably predetermined, and it simultaneously determines the distance of the yarn from the heated surface.
Such a heater is used, for example, in a false twist crimping machine.
However, also different applications are taken into consideration.
Heaters for heating advancing, thermoplastic yarns (synthetic filament yarns) false twist crimping machines include, in general, elongated rails which are heated to a certain temperature, and over which the yarn is advanced.
For the drawing and heat setting of a synthetic filament yarn, a heated tube is described in DE-AS 13 03 384 which is looped by the yarn in a steep helix. At the yarn outlet end, the tube is provided with a bead to prevent a movement in circumferential direction.
A thermoplastic material for the yarn includes in particular polyamide (PA6, PA6.6) or polyethylene terephthalate, but is not limited to these materials.
It is the object of the present invention to provide a yarn heating apparatus which is simple to assemble, and which makes it possible to vary the curvature of the yarn path within wide ranges and to ensure for each yarn path and in all points of the yarn path a distance from the surface, which is independent of the selected curvature.